| 摘要 |
<p>PURPOSE:To perform transmission to each repeating device securely at low cost through simple constitution, by sending out a DC signal with an optional polarity from one terminal of each balanced couple of cores together with a control signal of optional frequency when bringing repeating devices arranged on a transmission line under the remote control of a terminal equipment side; CONSTITUTION:From a constant current source 14, a DC signal is sent out to between input terminals (c) and (d) of a balanced couple of cores 2. The terminals of the balanced couple of cores 2 are looped, so the sent DC signal flow through Zener diodes 6 and 7 of each control signal output circuit in series. When the polarity of the input terminal (c) is positive, the voltage across the Zener diode 6 is a Zener diode of, for example, about 5 V and the voltage across the Zener diode 7 is a forward voltage of about 0.7V. Voltage detecting circuits 8 and 9 do not operate by the forward voltage, but operate by the Zener voltage, so only the voltabe detecting circuit 8 outputs a voltage detection signal (g) and a voltage detection signal (h) is not outputted. An AND gate 10 is therefore opened to output a control signal (e) as the 1st control signal (j) through the AND gate 10.</p> |
